1. Field of the Invention
The present invention relates to an information storage medium, and more particularly, to an information storage medium such as an optical disc, a method of managing replacement information, a recording/reproducing apparatus and a host apparatus, that enable efficient use of an information storage medium.
2. Related Art
For rewritable information storage media, a spare area is typically provided in a data area for defect management. That is, if a defect occurs while user data is being recorded in a user data area (an area in the data area that excludes the spare area) or data recorded in the user data area is being reproduced, replacement data to replace defect data is recorded in the spare area.
For write-once information storage media, the above defect management technique is used in a logical overwrite (LOW). LOW is known as a method in which the write-once information storage media in the same manner as the rewritable information storage media. That is, to update data already recorded in the user data area, recorded data can be considered as defect data, and data to replace the recorded data can be recorded in the spare area by considering the recorded data as defect data. This makes data management easier since a host can access data using a logical address thereof and data for replacing the recorded data in the user data area can be overwritten at the same location by using the fixed logical address of the data recorded in the user data area and assigning a physical address corresponding to the fixed logical address to the data recorded in the spare area. In addition, a new method which implements LOW for defect management has been suggested to maximize the use of an information storage medium. In such a method, updated data can also be recorded in an unrecorded portion of a user data area in addition to a spare area on an information storage medium, and replacement information (replacement entry information) can be prepared accordingly.
Logical overwrite (LOW) for defect management will now be described with reference to FIGS. 1A and 1B as follows.
FIGS. 1A and 1B are reference diagrams of an example data area on an information storage medium used to illustrate a gap between a logical volume space and a physical volume space when a logical overwrite (LOW) for defect management is implemented.
Referring to FIG. 1A, a data area 100 includes a series of a spare area (SA) #1 110, a user data area 120 and another spare area (SA) 130, and data A is recorded from a start address of the user data area 120.
When the data A already recorded in the user data area 120 is updated, as shown in FIG. 1B, updated data A is recorded next to the data A to replace the data A recorded in the user data area 120. By recording data to replace data recorded in the user data area 120 in an unrecorded area of the user data area 120, both the data A and the updated data A exist in the physical volume space, and the updated data A exists in the logical volume space. According to LOW, like in the case of rewritable information storage media, data can be updated in write-once information storage media without changing their logical addresses.
Since LOW defect replacement is performed in the spare area SA 110 or 130, or the user data area 120, replacement entries providing information on replaced states are required.
For conventional replacement entries, since there exist only replacement (defect) entries due to defect blocks on an information storage medium, an entry size of the replacement entries can be somewhat predicted, and thus the size of a defect list storing the replacement entries can be defined.
However, since an increase of the size of replacement entries due to LOW can result in an excessive increase of the overall size of the replacement entries that the defect list can store, an overflow of the defect list is likely to occur which can cause problems.
For the write-once information storage media, since the defect list is recorded in a subsequent unrecorded area, and not re-recorded at the same location when the defect list is updated in a defect management area, an updated area of the defect list is not necessarily needed if a unit of the defect list is smaller. Thus, the number of times when updating is performed can be increased.
For rewritable information storage media, file system data is typically assigned to a predetermined close area such as a start or end portion of a logical volume space. When a rewritable information storage medium is loaded in a drive system, the file system data should be read first, and by assigning the file system data to the predetermined close space, a reproducing time of the file system data can be minimized. For rewritable apparatuses, a state of the predetermined close area of the logical volume space can be physically maintained due to a rewriting function even if a portion of the file system data is updated.
However, for write-once information storage media, when a portion of the file system data is updated by LOW, even if a logical location of the updated file system data is the same, there is no alternative but to change a physical location of the updated file system data. Because of this requirement, unlike for the case of the rewritable information storage media, there is no choice but to separately assign physical locations of the file system data of the write-once information storage media even if the file system data is logically assigned to a predetermined close area. As a result, a significant amount of time is required to reproduce the file system data when a write-once information storage medium is loaded in a drive system.
Likewise, a report of replacement entries from a drive system or a similar method can be used to determine a state in which file system data or data used for a similar purpose is physically dispersed. In this situation, a reproducing time of the file system data can be minimized, when a host such as a file system (FS) drive reassigns the dispersed data to a predetermined close area. In this case, the existing file system data should be deleted due to the reassignment. However, the replacement entries of the deleted data still remain in the physical volume space. Thus, when this state repeats, the defect list easily overflows due to useless replacement entries. Alternatively, in a case where the size of the defect list is not fixed, the defect management area can be quickly exhausted due to an increase of the size of the defect list. As a result, an effective use time of an information storage medium is decreased, which can cause an inconvenience to a user. Accordingly, needed are new techniques to leverage a defect list for defect management efficiency.